Similar Problem. But only if I play COOP.
If I play any map in COOP mode alone, everything works fine.
But no matter which map or how many AIs - whenever a friend of mine joins me, we are able to play the map for between 20 and 40 minutes. Then CTD. Always.
There are also other bugs appearing only in coop when I play with someone that dont appear when I play alone (also coop mode), like flags that can't be captured although the bar is already full blue. But this is a known bug I think.
Nevertheless, those ctds are really annoying because you can't finish a single round together without being cut off at some place.
And no, hardware really cant be the problem.